Several publications and patent documents are cited throughout the specification in order to describe the state of the art to which this invention pertains. Each of these references is incorporated herein as though set forth in full.
Coronary artery disease (CAD) is a major cause of morbidity and mortality, requiring bypass surgery or angioplasty in almost 1,000,000 patients/year in the USA. While some of these patients form collateral vessels as alternative pathways for blood supply, thus ameliorating or preventing ischemic myocardial damage, many do not form the vascular networks to sufficiently compensate for the loss of the original blood supply. Accordingly, many patients could be helped by the development of compositions and methods which would accelerate natural processes of post-natal collateral vessel formation. Such approaches are broadly referred to as “therapeutic angiogenesis”, and encompass both angiogenesis (which strictly speaking refers to capillary sprouting) and arteriogenesis (the maturation and enlargement of existing vessels) (Isner J M and Asahara T. J Clin Invest. (1999) 103:1231-6; van Royen N, et al. Cardiovasc Res. (2001) 49:543-53.)
An emerging therapeutic approach is the use of stem and progenitor cell transplantation to improve angiogenesis. Endothelial progenitor cells (EPCs) are cells present in bone marrow or peripheral blood which co-express stem and progenitor cell markers like CD34 or AC133, as well as endothelial markers like VE-Cadherin and VEGF-Receptor-2 (KDR) (Rafii S., J Clin Invest. (2000) 105:17-9.) EPCs and hematopoietic stem cells (HSCs) are thought to be derived from a common “hemangioblast” precursor (Ribatti D, et al. J Hematother Stem Cell Res. (2000) 9:13-9; Choi K. J Hematother Stem Cell Res. (2002) 11:91-101; Eichmann A, et al. J Hematother Stem Cell Res. (2002) 11:207-14.) Interestingly, the cell surface marker CD34 is only found on either hematopoietic stem/progenitor cells or endothelial cells (Rafii S., J Clin Invest. (2000) 105:17-9,) which may be a reflection of the common origin of these two cell lineages. In addition to the shared “hemangioblastic” ancestry between HSCs and endothelial cells, HSCs have also been suggested to trans-differentiate into either endothelial progenitor cells or mature endothelial cells (Kang H J, et al. Br J Haematol. (2001) 113:962-9; Quirici N, et al. Br J Haematol. (2001) 115:186-94; Gehling U M, et al. Blood. (2000) 95:3106-12.) The recent discovery of circulating smooth muscle progenitor cells, and the potential of HSCs to differentiate into smooth muscle cells (Sata M, et al. Nat Med. (2002) 8:403-9; Simper D, et al. Circulation. (2002) 106:1199-204) may suggest yet another novel and intriguing link between the hematopoietic and vascular cell lineages, now in the context of smooth muscle cells.
Animal studies using hindlimb ischemia or myocardial ischemia models in immune deficient rodents have demonstrated that transplantation of about 106 peripheral blood derived EPCs (Kawamoto A, et al. Circulation. (2001) 103:634-7; Kalka C, et al. Proc Natl Acad Sci USA. (2000) 97:3422-7) can result in increased angiogenesis. Remarkably, labeled peripheral blood derived EPCs appear to home preferentially to ischemic areas and incorporate into foci of neovascularization (Kawamoto A, et al. Circulation. (2001) 103:634-7; Kalka C, et al. Proc Natl Acad Sci USA. (2000) 97:3422-7.) In addition to the above-mentioned studies on peripheral blood-derived cells, EPCs derived from bone marrow, unpurified bone marrow mononuclear cells, and HSCs have also been shown to enhance angiogenesis or show endothelial differentiation in vivo in a variety of animal models of ischemia (Kocher A A, et al. Nat Med. (2001) 7:430-6; Shintani S, et al. Circulation. (2001) 103:897-903; Fuchs S, et al. J Am Coll Cardiol. (2001) 37:1726-32; Kamihata H, et al. Circulation. (2001) 104:1046-52; Orlic D, et al. Proc Natl Acad Sci USA. (2001) 98:10344-9; Jackson K A, et al. J din Invest. (2001) 107:1395-402.)
Transplantation of hematopoietic stem cells (HSCs) into patients with myelodysplastic disorders or following myeloablative radiochemotherapy is the most widespread application of stem cell therapy. HSCs are characterized by surface markers like CD34, and constitute less than 0.5-1% of the bone marrow (Gunsilius E, et al. Biomed Pharmacother. (2001) 55:186-94,) which is currently the primary source of transplantable HSCs in the clinical setting. The limited availability of HLA-compatible siblings (less than 30%) (Tabbara I A, et al. Arch Intern Med. (2002) 162:1558-66) has resulted in frequent use of non-HLA-compatible siblings as donors. Although recently there has been some success in the reduction of complications following allogeneic transplantation of HSCs, chronic graft versus host disease and engraftment failure of allogeneic cells remains a significant clinical problem (Tabbara I A, et al. Arch Intern Med. (2002) 162:1558-66.) Autologous stem cell transplantation circumvents these complications, however, autologous cells from the bone marrow or peripheral blood may be contaminated by malignant cells (Hahn U and To L B, In: Schindhelm K, Nordon R, eds. Ex vivo Cell Therapy. San Diego, Calif.: Academic Press; (1999) 99-126.)
While the concept of using autologous peripheral blood derived EPCs in patients seems attractive, based on animal studies, one would need 12 liters of blood from a patient to isolate enough cells to achieve a pro-angiogenic effect (Iwaguro H, et al. Circulation. (2002) 105:732-8.) This amount of blood is not readily available in a clinical setting. Human studies that have used of bone marrow cell transplantation in ischemic patients (Strauer B E, et al. Dtsch Med Wochenschr. (2001) 126:932-8; Tateishi-Yuyama E, et al. Lancet. (2002) 360:427-435) suggest that human angiogenic cell therapy requires at least cell numbers of 107 to 109, depending on the degree of stem cell purity as well as the optimal delivery method.
The discovery of pluripotent cells in the adipose tissue (Zuk P A, et al. Tissue Engineering. (2001) 7:211-28) has revealed a novel source of cells that may be used for autologous cell therapy to regenerate tissue. The pluripotent cells reside in the “stromal” or “non-adipocyte” fraction of the adipose tissue; they were previously considered to be pre-adipocytes, i.e. adipocyte progenitor cells, however recent data suggests a much wider differentiation potential. Zuk et al. were able to establish differentiation of such subcutaneous human adipose stromal cells (ASCs) in vitro into adipocytes, chondrocytes and myocytes (Zuk P A, et al. Tissue Engineering. (2001) 7:211-28.) These findings were extended in a study by Erickson et al., which showed that human ASCs could differentiate in vivo into chondrocytes (Erickson et al. Biochem Biophys Res Commun. (2002) 290:763-9) following transplantation into immune-deficient mice. More recently, it was demonstrated that human ASCs were able to differentiate into neuronal cells (Safford K M, et al. Biochem Biophys Res Commun. (2002) 294:371-9).
Given the many applications of stem cell therapy, a need exists in the art for providing a more abundant and practical source for such stem cells, and for enhancing the potential therapeutic benefit and route of administration of these cells.